Regioselective formation of kojic acid-7-o-alpha-d-glucopyranoside by whole cells of mutated Xanthomonas campestris

Whole cells of mutated Xanthomonas campestris were successfully used as a biocatalyst for the glucosylation of kojic acid. Suitable carbon and nitrogen sources and the pH for the cultivation of the mutated cells at 30 °C were identified for maximum conversion. Using 0.1 g of the cells, 80% conversion was obtained after 28 h at 30 °C and by using maltose as the acyl donor at a molar ratio of 1:8. Under the same conditions, the use of wild type cells resulted in 13% conversion only. 1D NMR and 2D shift-correlated NMR (1H × 1H-COSY, 1H × 13C-COSY) analysis showed that the product was kojic acid 7-o-alpha-d-glucopyranoside.